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Commercial floor area calculator

Enter the measurements of the home and its outbuildings: the calculator applies the coefficients of Italian Presidential Decree 138/98 and shows the commercial floor area (superficie commerciale) item by item.

Main area
m²
Rooms, kitchen, bathrooms, hallways and corridors, measured including walls.
Cellars, attics and similar
m²
Reached by an internal staircase or door.
m²
Reached only from shared areas or from outside.
Balconies, terraces and similar
m²
You step out directly from the rooms of the home.
m²
For example a terrace reached only from the shared stairs.
Outdoor space
m²
Outdoor area for the exclusive use of the property.
Indicative value (optional)
€/m²
Multiplies the commercial floor area by a reference price, for example local market prices.

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Commercial floor area
0 m²

Enter the measurements: the result updates as you type.

This is an indicative estimate. It is based on the data you entered and on the rules in force on 23 October 2026. It is not advice and does not replace the opinion of the surveyor or architect who measures the property: always check the figures before using them in a deed. Terms of use

How the commercial floor area is calculated

In Italy, property prices are compared on the commercial floor area. The legal reference is Annex C of Presidential Decree no. 138 of 23 March 1998, which sets how much each part of the property counts.

The coefficients of Decree 138/98

  • Main rooms and direct service rooms (rooms, kitchen, bathrooms, hallways, corridors): 100%.
  • Cellars, attics and similar: 50% if connected to the home, 25% if not.
  • Balconies, terraces and similar: 30% up to 25 m² and 10% beyond, if connected; 15% and 5% if not.
  • Private garden or outdoor area: 10% up to the area of the main rooms, 2% beyond. For villas and detached houses (R/2) only the part beyond five times the main rooms counts.

Areas with a ceiling height below 1.50 m are not counted, and the result is rounded to the square metre. Cellars, balconies and garden together cannot exceed half of the main rooms: the Agenzia delle Entrate applied this limit in ruling no. 306 of 2019, and the calculator applies it automatically.

An example

A 95 m² gross flat with a 12 m² connected balcony and an 8 m² separate cellar: 95 + (12 × 30%) + (8 × 25%) = 95 + 3.6 + 2 = 100.6 m², rounded to 101 m² commercial floor area.

Frequently asked questions

What is the commercial floor area of an Italian property?

It is the size Italian listings and valuations are based on, and the one the price per square metre refers to. It starts from the gross internal area, walls included, and adds a share of balconies, cellars and outdoor space, each with its own coefficient. That is why it is always larger than the walkable area.

How are walls counted?

Under Annex C of Presidential Decree 138/98, internal and external walls count in full up to 50 cm thick; walls shared with other units or with common parts count at 50%, up to 25 cm. Enter the area with the walls already included.

How much does a balcony add?

A balcony or terrace that opens onto the home counts at 30% for the first 25 m² and 10% beyond that. If it is not connected to the home, the rates are halved: 15% and 5%.

Is a garage included?

No. Garages and parking spaces are usually separate cadastral units (category C/6) and are valued separately, at their own price. The calculator covers the home and its outbuildings.

Can I use the result in a deed or a survey?

No. The calculator gives an estimate based on the measurements you enter. A deed, a valuation or a land registry filing needs measurements taken by a qualified surveyor.

Sources

Presidential Decree no. 138 of 23 March 1998, Annex C (Gazzetta Ufficiale no. 108 of 12 May 1998); Agenzia delle Entrate, ruling no. 306 of 23 July 2019. Criteria updated on .